Reliable high-speed, high-power switching has a wide variety of applications such as radar and communications transmitters, ion implantation, particle accelerators, induction heating, and materials processing. Applications of high-speed, high-power switching require consistent, controllable, rapid, and cost-effective switching of high levels of electrical power. The components and technologies currently available to support these high-power switching applications were developed in the 1930's and 1940's. Despite the revolution in cost and performance that solid state technology has brought to nearly every other realm of electronics, progress with solid state high voltage and high power switching devices has been slow and improvements have been modest.
For example, vacuum switch tubes or thyratrons, alone or in combination with Pulse Forming Networks (PFNs) and pulse transformers, have been used to switch high voltage power supplies and high voltage loads, such as gyroklystrons. The non-ideal behavior of tube switches, however, results in numerous undesirable characteristics, such as large effective on-voltage drop, limited current capability and speed, limited Pulse Repetition Frequency (PRF) capability, high maintenance, and complex driving and protection circuitry. Nevertheless, such switches have provided a nearly exclusive solution to the problem of high-voltage switching until recently.
Typical tube switches use a single device to switch the entire switching voltage. Consequently, the high voltage capability of most tube switches is limited to the high voltage capability of a single tube. This limits the reliability and flexibility of high voltage systems using these tubes. Thus, as new system requirements extend to higher voltage or power, the use of tubes becomes increasingly problematic.